Changes in fungal and bacterial diversity over a peanut soil moisture gradient

Background and aims

The soil microbiome is vital to plant health. Drought can affect the abundance of soil microbial communities, plant productivity, and plant health. Peanut (Arachis hypogaea) is an important crop worldwide that is at risk of infection with Aspergillus flavus during heat and drought, which increases the risk of carcinogenic aflatoxin contamination. We hypothesized that varying soil moisture would shift microbial composition and reveal drought-adapted microbes possibly capable of competing with A. flavus.

Methods

Two soils from fields with a history of peanut production were collected at Wiregrass Research and Extension Center, Headland, Alabama. The soils were placed in polyvinylchloride tubes inside a growth chamber at 29 °C. Five water regimes in a gradient from dry to wet were applied to the soils for nine weeks. They were sampled every other week, and the ITS1 for fungi and 16S rRNA gene for bacterial amplicons were sequenced to determine the effect of the moisture treatments on the microbial communities.

Results

Time and moisture treatments impacted both bacterial and fungal community structure and composition. Bacterial and fungal richness and evenness decreased and never fully recovered over nine weeks. Additionally, bacterial and fungal communities were also influenced by time and moisture treatments. Specifically, the bacterial phylum Actinobacteria thrived in drier treatments, while Proteobacteria were more abundant in moist treatments.

Conclusion

We concluded that dry moisture treatments do influence bacterial and fungal communities in peanut soils, with Actinobacteria as potential microbes of interest to support peanut growth, increase drought tolerance, and disease resilience.